Automatic Transmission Shift Lock Control System

The automatic transmission shift lock control system is a safety device that prevents an inadvertent shift out of PARK when the engine is running. The driver must press the brake pedal before moving the shift lever out of the PARK position. The system consists of the following components:

• The automatic transmission shift lock control solenoid
• The body control module (BCM)
• The powertrain control module (PCM)

The body control module (BCM) controls the ground circuit of the shift lock control solenoid. The following conditions must be met before the BCM will supply a ground to the shift lock control solenoid:

• The ignition is in the ON position.
• The powertrain control module (PCM) sends a class 2 message to the BCM indicating the transmission is in the PARK position.
• The PCM receives a brake applied input from the brake light switch and sends a class 2 message to the BCM indicating the brake pedal is depressed.

With the ignition in the ON position the shift lock control solenoid is supplied battery voltage from the ign 1 fuse. When BCM supplies a ground to the control circuit of the automatic transmission shift lock control solenoid, the solenoid energizes, releasing the mechanical lock. This allows the driver to move the shift lever out of the PARK position.

Vehicles equipped with VTi variable transmission in cold weather temperatures below -25°C (-13°F) the PCM will send a class 2 message to the BCM preventing the operation of the shift lock control solenoid and the temperature gage light will flash. Once the transmission has warmed above -25°C (-13°F) the temperature gage light will stop flashing and normal shift lock control operation will resume.